Method of combining wastewater treatment and power generation technologies

ABSTRACT

Applicant&#39;s preferred embodiment utilizes municipal wastewater effluent to replenish a depleted geothermal field. Condensate produced by expanding steam produced in the geothermal field through a steam turbine-generator may be pooled with cooked water collected from said field, and then directed through a penstock from a higher elevation to a lower elevation where further energy is extracted through a traditional hydroelectric turbine-generator. The cooked water and condensate may be treated to produce potable water and/or distributed for public consumption either before or after being directed to the hydroelectric turbine-generator. The effluent is pumped up to the geothermal field during off-peak periods of electric consumption, and the hydroelectric generation is accomplished during periods of peak electric demand. A fraction of the effluent may be used as cooling water for the steam turbine-generator and its associated condenser before injection into the geothermal field. At least a portion of the pipeline to transport the wastewater effluent is preferably routed along an undisturbed riverbed and/or through an excavated tunnel.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 08/969,712, filed on Nov. 14, 1997 entitled “AMETHOD OF COMBINING WASTE WATER TREATMENT AND POWER GENERATIONTECHNOLOGIES”, which is a continuation of U.S. patent application Ser.No. 08/545,110, filed on Oct. 11, 1995 entitled “A METHOD OF COMBININGWASTE WATER TREATMENT AND POWER GENERATION TECHNOLOGIES”, now abandoned.

FIELD OF THE INVENTION

Applicant's invention deals with the utilization of wastewater effluentto revitalize a depleted geothermal field, and the combining of twopower generation technologies to provide overall system efficiencygains.

The two power generation technologies employed are geothermal powergeneration, where steam is obtained from thermal fields underneath thesurface of the earth, and hydroelectric generation, where energy isextracted from movement of a volume of water due to gravitational force.

The wastewater treatment phase of Applicant's invention capitalizes onthe injection of municipal waste effluent into the strata of thegeothermal field which supplies steam for power generation. Similarinjection methods utilizing brine solutions have been employedhistorically to assist in the yield of geothermal steam. Such injectionhas been necessary to lower the mineral content of the geothermal steamand fluids. Lower temperature brine is mixed with high temperature, highmineral brine to reduce mineral content and re-injected into the field.

In this case, waste effluent is injected into the strata to replenishlost water, not to lower mineral content. The water is recaptured ascooked water or geothermal steam that is utilized for power productionand treated to yield potable water.

Applicant's invention additionally deals with the laying of pipe orother conduit for the conveyance or transport of matter such as wasteeffluent or electrical current in a manner and place not otherwisepossible, or at significantly higher construction and/or maintenancecosts, while providing a potentially more direct alignment or route.

BACKGROUND OF THE INVENTION

Basic power generation technologies are generally grouped according tothe energy source used to produce electricity. Fossil fuels such ascoal, gas and oil are used to produce steam which is expanded through asteam turbine which, in turn, drives a generator thereby producingelectric power. Fuels can also be combusted as in a gas turbine, wherethe primary energy source is hot gas which again expands and drives agenerator. Nuclear power also uses a steam turbine-generator to convertsteam produced by a nuclear reactor into power. In the case ofgeothermal power generation, steam naturally produced by the earth isextracted and processed to an extent, for expansion again, in a steamturbine-generator, although at much lower temperatures and pressuresthan the aforementioned fossil fuels. While the efficiencies associatedwith the geothermal steam are much lower than that of the traditionalfossil fuels, the steam is essentially free, after the installed cost ofthe delivery infrastructure, compared to the cost of fossil fuelnecessary to produce like amounts of steam. Solar power has also beenused to boil water for steam as in Solar One, a plant near Dagget,Calif.

Technologies such as hydroelectric generation utilize the extraction ofpotential energy from water moved from higher elevations to lowerelevations, using the rush of falling water through a “Francis” or“Kaplan” impulse turbine in order to turn a generator and produceelectricity. There is no need to produce steam in such a system. Theimpinging force of the water acting on the water turbine provides theenergy to be extracted.

While naturally occurring energy sources such as sunlight or water are“free”, they can vary in supply. In dry years, less hydroelectricgeneration is available. On cloudy days, less solar power can begenerated. Where wind turbines are concerned, at least a mean windvelocity of 10 mph is required to justify installation, because if thereis no wind, power is not produced. Similarly, geothermal fields finallyexpend their available steam, rendering the massive distribution systemand generating equipment installed above the field useless. Utilitycompanies and power associations have traditionally attempted to managesuch systems: placing hydroelectric systems proximate to predictablewatersheds and by building reservoirs; installing arrays of windturbines in established zones of plentiful and predictable windcurrents; building solar plants in desert locations, etc.

Today, in an effort to increase generation thermal efficiencies,technologies are sometimes combined. The best and primary example ofsuch a combination is steam and gas turbine technology. In such asystem, a gas turbine is used to generate electricity, and concurrently,the exhaust gases, at nearly 950° F., are directed through a heatrecovery boiler to produce steam which is then expanded through atraditional steam turbine-generator. This combination dramaticallyincreases the overall thermal efficiency beyond that seen with eithergas or steam technology separately.

The aforementioned combinations are typically not available in thenaturally occurring energy resources.

Efforts to find other renewable energy sources to reduce dependence onfossil fuels have spawned alternate fuels including the burning ofagricultural waste such as wood chips, almond shells and rice hulls togenerate power. Used tires, municipal solid waste in the form of ascreened mass or refuse-derived fuel have also provided fuel for powergeneration. In the case of municipal solid waste, the fuel has beenexploited in large part to reduce the amount of waste sent to landfills.To say that the utilization of municipal wastes in the generation ofelectric power advances the common good would be an extremeunderstatement.

What is continually needed, then, are ways to extend or augment theavailability of renewable or natural resources beyond traditional systemefficiency improvements, in order to prolong available energy resourcesand reduce the dependency on fossil fuels. In conjunction, new methodsof utilizing municipal waste and its byproducts are also necessary toease the environmental impact of simple disposal, and to provide acleaner environment.

In Sonoma County, California, the world's largest geothermal powergeneration project has been operating for decades. The geothermal field,called the Geysers, was developed by major oil companies, and the giantpower generation utility Pacific Gas & Electric Company exploited thefield for electric generation, installing several steamturbine-generators, and leasing the resource field from the originaldevelopers. Other smaller utility companies have also leased portions ofthe field for production of electric power. Up to twenty-one units wereinstalled over the years.

In the past decade, the pressure and volume of geothermal energyavailable in the Geysers field has lessened continually. Pacific Gas &Electric has closed several of the existing units and has curtailedproduction of others. Plans to retire existing units have beenaccelerated, and staff has been reduced.

In the neighboring community of Santa Rosa, Sebastopol, Rohnert Park andCotati, millions of gallons of effluent are produced in the localwastewater treatment plant. Approximately 30 million gallons per day ofeffluent are produced in relatively close proximity to the Geysers.

The introduction of 30 million gallons per day of waste effluent would,over time, replenish the depleted steam resource of the Geysers. Theinfrastructure necessary to deliver this water to the Geysers willrequire a pipeline whose capital cost is not unlike that necessary toconstruct a penstock and/or dam for hydroelectric plants.

Also, environmentalists have warned that a conventional pipeline to ageothermal field could rupture and release wastewater into nearbycreeks. Additionally, a pipeline rupture could result in a substantialvolume of wastewater cascading down from a higher elevation, creating asafety hazard. In the case of the Geysers, the situation is exacerbatedby seismic activity.

SUMMARY OF THE INVENTION

Applicant's invention comprises a novel combination which utilizesmunicipal wastewater in such a way to revitalize a depleted geothermalfield while also taking advantage of available terrain to combinehydroelectric and geothermal power generation technologies in a waynever before attempted.

Wastewater effluent provided by the local municipalities would bedelivered to a geothermal field such as the Geysers via a pipeline. Atleast a portion of the pipeline is preferably routed along anundisturbed riverbed and/or through an excavated tunnel.

The effluent may be injected at various points in the geothermal field.Potential injection points include the existing wells which have beenexhausted of their geothermal steam.

According to Applicant's process, once the geothermal steam has beenexpanded in the turbines for the production of electricity, the spentsteam is condensed and then may be redirected to a holding pond forstorage. The stored condensate is transported to lower elevations via apenstock where energy is extracted in the form of electricity by ahydroelectric turbine-generator.

The cost of pumping the water back up the mountain can be partiallyoffset by the value of the power extracted in the same way as a typical“pump-storage” hydroelectric facility. In such a scheme, water is pumpeduphill during off-peak periods when the value of power is low. Thehydroelectric generation is accomplished during peak periods when thevalue of power is high, thereby providing a sound economic reason forpumping the water uphill in the first place.

The present invention also deals with the laying of pipe, along withother conduits, primarily for the conveyance of water such as wastewaterin a manner and place not otherwise possible, or at significantly higherconstruction and/or operational/maintenance costs, while providing apotentially more direct or convenient route. In one embodiment, thepresent invention permits unabated conduit inspection and maintenancepotential.

For example, the present invention provides a method of laying pipelinesubmerged on an undisturbed riverbed without requiring bed preparationtechnologies. One embodiment of the present invention provides forlaying shielded or unshielded pipe/cable/conduit (PCC) for theconveyance of fluids, particulate matter or electrical current whileresting submerged on an undisturbed riverbed, on the bottom of any bodyof water, across a swamp, a bog, areas of quick soil, or across anyother area of unstable material and/or spanning potholes, cavities ortrenches while fully or partially suspended, while requiring no beddingpreparation. The PCC shielding is provided to protect the PCC fromexternal damage from impacts, stresses, ground movements, beddingcavitations or erosions.

In another embodiment, the present invention provides a pipelineconstructed within a utili-tunnel. The utili-tunnel is preferablyprovided with a pipe breach flow-check.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a line diagram of the steps of Applicant's method of employingwastewater effluent in power generation technologies.

FIG. 2 is a schematic diagram of a steam turbine-generator and itsconnected cooling water and condenser system.

FIG. 3 is a cross-section of a primary pipe/conduit 11 with supportingsleeve sheathing 41 and supporting cable/rod 21, safety cable 22, andpull wire 31, constituting the ensemble when utilizing sleeve sheathing41.

FIG. 4 is a cross-section of a multiple pipe/conduit/cable (MPCC) 19assembly, with sleeve sheathing 41, supporting cable/rod 21, safetycable 22, and pull wire 31.

FIG. 5 is a cross-section of a primary pipe/conduit 11 with two-piecesupporting rings 51 with their cold forged rivets 54, a ring separatorwire 32 and supporting ring stops with set screws 33, along with pullwire 31, comprising the ensemble utilizing support rings 51 and nosleeve sheathing 41.

FIG. 6 is a profile of FIG. 5, showing a primary pipe/conduit 11, withtwo-piece supporting rings 51 with cold forged rivets 54, a ringseparator wire 32 with stops for each face of the supporting rings withset screws 33. (Not illustrated here is the supporting cable/rod 21,safety cable 22 and pull wire 31 of FIG. 5.)

FIG. 7A is a cross-section of a typical pipe/conduit/cable 11 ensemblewith sleeve sheathing 41 laid laterally to a stream flow and shelteredfrom the lateral stream flow by steel sheet piling 61 driven against iton its upstream side and driven into the undisturbed riverbed.

FIG. 7B is a cross-section of a typical pipe/conduit/cable 11 ensemblewith sleeve sheathing 41 (as shown in FIG. 7A) laid laterally to thestream flow and sheltered from the lateral stream flow by reinforcedconcrete or other rigid paneling 63 held in place by “H” cross-sectionsteel piling 65 driven into the undisturbed riverbed.

FIG. 8 is a plan view of a utili-tunnel entry.

FIG. 9 shows a cross-section of the utili-tunnel.

FIG. 10 shows a longitudinal utili-tunnel profile.

FIG. 11 shows a utili-tunnel summit profile.

FIG. 12 shows a utili-tunnel beginning profile.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A sewage treatment plant 10 provides effluent 5, for use in a geothermalsteam field such as the Geysers steam field 20, located at site 30. Alsolocated at site 30 are the following components, as shown in FIG. 1: asteam turbine-generator 50, a heat exchanger system 52, a holding pond46, an inlet to a penstock 44, and a piping system for carryingcondensate 62, effluent 5, steam 60 and cooked water 64 as describedbelow.

The effluent 5 is piped through a plurality of pumps 15 to site 30 whereit is routed in one of several directions. The effluent 5 may beinjected directly into the geothermal strata 40, located deep below thesurface of the site 30, or into the heat exchanger system 52, for use asa cooling medium. After use as a cooling medium in heat exchanger system52, the effluent 5 is injected into the geothermal strata 40. From thegeothermal strata 40, geothermal steam 60 is extracted through its owndistribution to the steam turbine-generator 50, where it is expanded andcondensed to produce electricity. From the steam turbine-generator 50,the condensate 62 is piped either to a holding pond 46, or to thegeothermal strata 40 where it is re-injected. Any fraction of thecondensate may be re-injected into the geothermal strata 40, or directedto the holding pond 46. The holding pond 46 stores condensate 62, forfurther use. Cooked water 64, also extracted from the geothermal strata40, is also piped to the holding pond 46. The condensate 62 and cookedwater 64 provide sterilized water that is void of all live bacteria,virus, and/or vegetation.

The condensate 62 and/or cooked water 64 is introduced into the holdingpond 46 sufficiently below its surface to avoid any contamination of theair due to vapors effected by contact with the geothermal strata 40. Theholding pond 46 provides the needed volume and pressure to be usefulwhen directed down penstock 44 to the inlet of the hydroelectricturbine-generator 70, where the potential energy is extracted in theform of electricity. After flowing through the hydroelectricturbine-generator 70, the condensate 62 and cooked water 64 areprocessed in water treatment system 80, consisting of filtration andchemical treatment to remove sulfur, arsenic, iron and dissolved solids.No organic contamination will exist after injection and recapture assteam or cooked water.

In another embodiment of the present invention, treatment of thefractions of cooked water 64 and/or condensate 62 to be directed to theholding pond 46 may first be treated to produce potable water, therebyeliminating potential problems stemming from a contaminated holdingpond. The potable water may then either be held and distributed forpublic consumption or directed down penstock 44 to extract the potentialenergy in the hydroelectric turbine-generator 70.

For example, condensate 62 and/or cooked water 64 can be piped to adistillation plant 90. Also, in the event of interruption ofre-injection of the condensate 62 from the heat exchanger system 52, theflow can be maintained via a bypass 53 of the re-injection well to flowcondensate to the distillation plant 90. The distillation plant 90 ispreferably located on the steam-field side of the site 30 and isprovided with water that is already near the flash point temperature.The temperature of the condensate 62 and cooked water 64 is such thatonly an incremental amount of heat, if any, is needed to convert liquidphase water to vapor, that is, any liquid can be economically heated toa vaporous state. The water vapor can then be condensed as distilledwater. The distilled water is then collected or directed down thepenstock 44, to the inlet of the hydroelectric turbine-generator 70,and, thence, to the water treatment system 80, for removal of anycontaminants dissolved or suspended in the distilled water en route tothe water treatment system. Also, in the event that the return line tothe penstock 44 ceases to vacate, causing a stoppage of the flow fromthe distillation plant 90, the plant flow may be temporarily diverted tothe holding pond 46.

Steam turbine-generators employ cooling water for a variety of reasons,but a chief application is in the condensing heat exchanger system 52,which is flexibly connected to the exhaust of the steamturbine-generator 50, as shown in FIG. 2, and which usually receives itscooling water from a cooling tower. It is possible that traditionalcooling towers may be reduced in size or even eliminated by using thelarge volume of available effluent for cooling. The condensing heatexchanger 52 creates a relative vacuum in the low-pressure stages of thesteam turbine-generator 50, helping the expansion of the steam 60through the system.

One embodiment of the present invention enables pipe/cable/conduit (PCC)to be laid within inundated or across unstable areas without the need ofprior excavation, trenching or other ground preparation and withoutbedding, while still providing stability and protection to the PCCagainst damage. The technology of this invention permits the use of anunlimited selection of kinds and types of primary and secondarypipes/conduits 11 and 12 in the form of rigid, supple, sectioned orspooled with coupled, screwed or mechanically jointed ends along withcable conduits 14, 16 and 17 and collectively referred to hereinafter asmultiple pipe/cable/conduit (MPCC) 19 for the transport of fluids,particulate matter, electric current and/or communication signals, andthese types and kinds may be interchangeable as the particular need mayarise, and none of which would be subject to damage subsequent to theirbeing laid due to their being secured by an engineered supporting cableor rod 21 and protected by a sleeved sheathing 41. The assembly will nowbe described in more detail.

The MPCC 19 is to be sleeved by a larger diametered housing as asheathing 41, and one or more rods and/or cables 21 installed betweenthe MPCC 19 and the sheathing 41 for semi- or intervaled suspensionand/or restraint of the ensemble from flexing action, and is alsoaccompanied by a pull wire 31 strung between the MPCC and the sheathingto provide a mechanism for pulling the supporting cable or rod 21through, or for its replacement, subsequent to the time of assembly andinstallation/placement.

The assembly also comprises couplings/ties. The couplings or ties at theends of the rod and/or cables 21 and 22 are preferably wrapped toprevent them from becoming snagged on the ends of the lengths of theMPCC 19 whenever any of the rod and/or cables 21 and 22 would bewithdrawn for repair or replacement.

Protection of the MPCC 19 is provided by the sheathing 41, and itsspecifications would vary to adequately suit the anticipated conditionsto which the MPCC would become subjected.

The MPCC 19 is to be protected in its entirety from damage by beingencased by a sleeve sheathing 41 and it being the intent that thesheathing 41 shield the MPCC 19 from the river current, any impacts fromtraveling debris carried by any river current or from any blows causedby man, or the like. The sleeve sheathing 41 can be constructed ofwhatever durable material to suit and which is available under eachinstallation circumstance. The sleeve sheathing 41 may be sealed at theends or left open to suit the nature of the MPCC 19 and whatever is tobe transported. Preferably, the material should be capable of beingreadily uncoupled if its sections are to be jointed. The inside diameteror opening should be such to be permitted adequate clearance from theMPCC 19 to permit the installation of the rod and/or cables 21 and 22and the pull wire 31 and subsequently to be readily withdrawn whenrequired.

Tension rod or cables 21 and 22 are to be installed to provide supportfor the MPCC 19 and restraint from tensile separation or compressionshifting and/or flexing stresses of the MPCC as a result of fluctuationsin the river current or from ground movements. The cables 21 and 22 canbe standard metal wire cable or any durable waterproof multiple-strand,non-metallic material capable of sustaining high, continuous tensileloading without elongation and/or failure. The diameter of the cable orrod 21 should be that which would be required to include a safetyfactor, as normally would be determined by the MPCC 19designer/engineer, and the rod and/or cables 21 and 22 would be attachedto anchors in, ashore and/or submerged within the body or area beingtraversed. The clearance between the MPCC 19 and the sleeve sheathing 41may not be void of water; therefore, the ends of the rod and/or cables21 and 22 should be allowed to protrude through/from the sheathing 41 tobe fastened to the anchors.

The rod and/or cables 21 and 22 can be tensioned to suit, by whatevermechanical or hydraulic means from the various anchor sites/points alongthe MPCC 19 alignment.

If more than one cable or rod 21 is utilized, all could be at reducedtension to that of the primary cable or rod 21, to act only as a safety.For example, the cable 22 could be provided in the event of damage tothe primary cable or rod 21.

The ends of the rod and/or cables 21 and 22 located within the sleevesheathing 41 should be coupled by connectors and should be wrapped toprovide their unobstructed passage over/past any end joint of the MPCC19.

The pull wire 31 is preferably a metallic or multiple-strand,non-metallic cord with high tensile strength installed along side theprimary support rod or cable 21 at the time of assembly to be used topull through any replacement supporting rod or cable 21 in the event ofdamage to the primary rod or cable 21. The pull wire 31 need not be leftunder tension.

In an alternative embodiment, when protective sheathing 41 for the MPCC19 is not being utilized, regularly spaced supporting rings 51 aroundthe MPCC 19, as shown in FIG. 5, are installed for the rod and/or cables21 and 22 to support the MPCC 19. The rings or bands 51 may be of metalor non-metallic material and can be one-piece fabrication; however,those of two or more pieces or open ended may be joined by cold forgedrivets 54 or otherwise united into an assembly without the applicationof heat, as shown in FIG. 5, and pre-drilled to accommodate beingthreaded by a ring separator wire 32.

The supporting rings/bands 51 should be allowed to slide longitudinallyalong the MPCC 19, but then become stopped at regular intervals bysupporting ring/band separator stops 33 on the supporting ring/bandseparator wire 32 threaded through pre-drilled holes through the rings51, utilizing crimped clips or sleeves with set screws 33 to the wireafter the stops have been placed against each of the faces of theseparating rings/bands 51, as illustrated in FIG. 6.

The ends of the supporting rod(s) or cable(s) 21 and 22 are to befastened to anchors installed at regular intervals, or wherever thephysical circumstances require to accommodate the MPCC 19 alignment. Theanchors can be pre-cast or constructed in place using poured concrete,concrete block, stone or brick masonry, be screwed or driven into theground and/or using marine dolphins or piling to secure the MPCC 19ensemble.

The system also provides bridging between anchors. The MPCC 19 can beinstalled utilizing marine dolphins, floats, pontoons, and/or buoys asanchors, where the bottom of the body or area being traversed isunknown, not readily accessible, and/or is too unstable to permit anybedded type of anchor construction.

The system provides accessibility and the ability to raise the MPCC 19.The anchor ends of the MPCC 19 can be made readily accessible at any ofthe anchor sites/points and can then be made readily capable of beinguncoupled and raised for inspection, change, and/or repair, and thenre-laid to rest without difficulty.

It is preferable that the ensemble be laid longitudinally versuslaterally to any river current or flow to minimize externally producedtension upon the MPCC 19 caused by the current, to avoid cavitationunder the sleeve sheathing 41, and to avoid flank impacts by currenttransported objects.

Additional pipeline shielding is preferably provided to address the needto shield the MPCC 19 when it lies laterally to the current of the riveror stream, as would normally be found at the points of ingress to, oregress from, the stream and in areas which would be significantly awayfrom eddy areas along the shorelines. The additional shielding isprovided by deflectors.

As shown in FIGS. 7A and 7B, the shielding is meant to protect the fullprofile of the MPCC 19 by installing deflectors, constructed of sheetpiling 61 driven into the undisturbed riverbed, or of a pre-constructedfabrication of panels 63, such as of steel reinforced concrete retainedin place by “H” cross-section steel piling 65 driven into the riverbedwithout excavation or other disturbance of the riverbed, installed alongthe upstream side of the MPCC 19, and battered by a factor of alpha fromthe plumb in an amount to be computed and made directly proportional tothe magnitude of the maximum anticipated current velocity of the riveror stream during flood and with the top edge of the panel being highenough above the top of the MPCC 19 to cause a vertical deflection ofthe flow up-and-over the top of the MPCC 19, and thereby preventingcavitation under the MPCC 19 and/or deflector 61 or 63 in addition toproviding the MPCC 19 complete protection from debris and the continuouslateral hydraulic pressure loading of the stream flow, which couldadversely deflect the MPCC 19, as well as exert potentially excessivetensile, or compressive, stress to the MPCC 19 and to its supporting rodor cable 21.

Such preventative measures should be taken wherever alignments of theMPCC 19 lateral to the current flow would not be sheltered by eddycurrents normally found along shorelines. The deflectors 61 or 63 aidthe preservation of the MPCC 19 within the hostile environment normallyexpected for the implementation of the invention. The deflectors 61 or63 render that environment compatible to the utility and long lastingpotential to its installation.

Laying/placement of the MPCC 19 is adaptable. The technology of thepresent invention permits the ensemble of the MPCC 19 with sheathing 41,rod and/or cables 21 and 22 and pull wire 31 to be laid to rest on theundisturbed bottom of any body of water, across any area of quick soil,swamp, bog, or to be suspended between any two or more points, and/orlaid interchangeably above and below the aqueous surface of any of thesetraversed areas without ground or bedding preparation being required.The MPCC 19 support method can be readily alternated from rod and/orcable support with sleeve shielding to rod and/or cable with rings/bandssupport, then readily reverted thereafter, particularly when inproximity to an anchor, without difficulty or limitations. Thedeflectors 61 or 63 are provided to protect the MPCC 19 installationwhen needed.

In another embodiment, the present invention provides for the conveyanceof water such as wastewater or other pumpable fluids, as well asutilities such as electricity, through a mountainous terrain, or othersites not readily accessible for pipeline construction, by way of atunnel housing any number of utility lines/pipes/conduits and referredto as a utili-tunnel.

The purpose of the utili-tunnel is to make it possible to lay conduitstraversing areas not readily compatible to such construction,particularly in seismically active locations. Preferably, a “pipe breachflow-check” incorporated into the structure of the utili-tunnel providesprotection against damage resulting from flooding in the event of a pipebreach.

As shown in FIG. 9, the utili-tunnel has a crown (ceiling) 114, forexample, twelve feet high, and an eight-foot width, for optimum utility.Construction would initiate typically by excavating the crown 114,followed by excavating (lowering) the invert (floor) 112 to provide thehead clearance desired.

Depending upon the type of soil being excavated, a concrete or groutliner may, or may not, be needed. If provided, the liner is preferablyput in place as the tunnel excavation advances.

Preferably, a pipe breach flow-check 130 is provided, as shown in FIG.8. If the utili-tunnel is inclined and a pipe breach occurs, the flowout of the tunnel portal (entry) 110 could become catastrophic to theadjoining landscape. This condition can be averted by designing andconstructing what is termed a “pipe breach flow-check” 130 in theutili-tunnel. The pipe breach flow-check 130 comprises a lateral tunnel131 commencing near the portal having the lowest tunnel elevation.

The lateral 131 would be of the same configuration as the main tunneland would daylight (exit) to the surface terrain. The main tunnel 110between the portal and this lateral would then be plugged 119, as shownin FIG. 8.

The utility of this uniquely configured pipe breach flow-check 130 isthat the hydraulic hammer associated with the burst and downward flow ofwater following a breach travelling down the utili-tunnel to exit thetunnel would slam against the plug 119. Subsequent to that impact, thewater would then flow through the lateral 131, without causing impactdamage. This feature is of particular importance when constructed inareas subject to strong seismic activity.

One or more pipes can be routed through the utili-tunnel. As shown inFIG. 9, the pipe(s) should be positioned close to the wall of the tunneland supported by cradles 120, spaced evenly at intervals so as tominimize sag in the pipe. Strapping the pipe to the cradles is optional.

Conduits and electric or communication cables can also befastened/mounted to racks 122 fastened to the upper walls of theutili-tunnel, as shown in FIG. 9. Lighting can also be provided. Tunnelillumination can be achieved by mounting a lifeline 126 of caged lightsto the center of the crown of the utili-tunnel.

Additionally, ventilation can be provided for the interior of theutili-tunnel. Ventilation within the utili-tunnel can be achieved bywall and/or crown mounting of a duct 124, commencing from the portalsand/or from vertical shafts to the surface. Fans can then be positionedwithin the ducts to control air movement. In anticipation of seepageinto the utili-tunnel, a paved gutter 116 can additionally beconstructed in the center of the tunnel invert (floor) 112.

One or more pump stations are provided in conjunction with theutili-tunnel. In one embodiment, pump stations 150 can be constructedinside the tunnel. For example, most strategically would be to place onepump at the portal containing the pipe breach flow-check lateral 131, asshown in FIG. 8.

Other pumps can be installed either straddling or alongside of the pipeby excavating alcoves to suit. Electrical power to the pumps can beracked and/or dropped via shafts from the surface.

Construction of the utili-tunnel has various advantages. Utili-tunnelconstruction can be very practical and economical when traversingmountainous terrains and/or when extreme climactic conditions and therisk of vandalism exists. Various other and more specific advantages areas follows: (a) inspection of the pipes, conduits and cables can beconducted at all hours, without concern for adverse weather conditions;(b) no excavations are needed to expose any of the utility lines inorder to conduct inspections or repairs; (c) clearance 118 along thepipe(s) 120 can be such to permit the use of a golf cart to travel theentire length of the utili-tunnel; (d) repairs can be conducted at allhours without hindrance; (e) the utility lines would not encroach onprivate lands and/or facilities on the surface; (f) public access couldbe avoided; (g) the interior of the utili-tunnel would not be subject tofreezing and/or snow; and (h) when constructed with a pipe breachflow-check, the utili-tunnel can be constructed and utilized in areas ofpotentially high or intense seismic activity.

The technology associated with the MPCC 19 and/or utili-tunnel of thisinvention consists of mechanical assemblies constructed from commonexisting and readily available materials, and requiring no sophisticatedworkmanship to assemble or skill to lay or install, other than what iscommon knowledge to any experienced pipeline, pile driving, excavatingand concrete workers. The technology provides the means of selecting theshortest possible pipeline route/alignment for the laying of the MPCC 19and/or utili-tunnel and which could not otherwise be accessible,available or traversable, while making the pipeline less susceptible todamage after having been laid and potentially at a lower constructionand/or maintenance cost.

While the invention has been described in connection with what ispresently considered the most practical and preferred embodiments, it isto be understood that the invention is not limited to the disclosedembodiments but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the scope ofthe appended claims.

1. A method of employing wastewater effluent in power generationcomprising the steps of: delivering wastewater effluent to a geothermalsteam field; injecting said effluent into said field; collecting steamfrom said field; extracting energy in the form of electricity from saidsteam by expansion in a steam turbine-generator system thereby producingcondensate; and distilling at least a fraction of said condensate toproduce potable water.
 2. A method according to claim 1 furthercomprising the step of: pumping said effluent to said geothermal steamfield through a piping system.
 3. A method according to claim 2 wherein:said pumping is performed in at least one stage.
 4. A method accordingto claim 1 further comprising the step of: directing at least a fractionof said condensate to a lower elevation by force of gravity, through ahydroelectric turbine-generator, extracting energy in the form ofelectricity.
 5. A method according to claim 4 further comprising thestep of: directing other than said fraction of said condensate to aholding pond.
 6. A method according to claim 4 further comprising thestep of: treating said condensate exiting said hydroelectricturbine-generator to produce potable water.
 7. A method according toclaim 1 further comprising the steps of: distilling cooked watercollected from said field; and directing at least a fraction of saidcooked water to a lower elevation by force of gravity, through ahydroelectric turbine-generator, extracting energy in the form ofelectricity.
 8. A method according to claim 7 further comprising thestep of: treating said cooked water exiting said hydroelectricturbine-generator to produce potable water.
 9. A method according toclaim 2 wherein: at least a portion of said pumping system is routedalong an undisturbed riverbed.
 10. A method according to claim 2wherein: at least a portion of said piping system is routed through autili-tunnel.
 11. A method according to claim 1 further comprising thestep of: distributing said potable water for public consumption.
 12. Amethod of employing wastewater effluent in power generation comprisingthe steps of: delivering wastewater effluent to a geothermal steamfield, said delivery being accomplished by at least one stage of pumpingsaid effluent through a piping system; injecting said effluent into saidfield; collecting steam from said field; extracting energy in the formof electricity from said steam by expansion in a steam turbine-generatorsystem thereby producing condensate; re-injecting a fraction of saidcondensate into said geothermal steam field; and distilling a fractionof said condensate producing potable water.
 13. A method according toclaim 12 further comprising the step of: directing a fraction of saidcondensate to a lower elevation by force of gravity in a penstockthrough a hydroelectric turbine-generator, extracting energy in the formof electricity.
 14. A method according to claim 12 wherein: said pumpingof said effluent takes place during off-peak periods of electricityconsumption; and said hydroelectric generation is accomplished duringpeak periods of electricity consumption.
 15. A method according to claim12 further comprising the step of: distributing said potable water forpublic consumption.
 16. A method according to claim 12 wherein: at leasta portion of said pumping system is routed along an undisturbedriverbed.
 17. A method according to claim 12 wherein: at least a portionof said piping system is routed through a utili-tunnel.
 18. A method ofemploying wastewater effluent in power generation comprising the stepsof: delivering wastewater effluent to a geothermal steam field;injecting said effluent into said field into at least one existing steamwell which has been substantially exhausted of geothermal steam;collecting steam from said field; and extracting energy in the form ofelectricity from said steam by expansion in a steam turbine-generatorsystem.
 19. A method according to claim 18 further comprising the stepof: pumping said effluent to said geothermal steam field through apiping system.
 20. A method according to claim 18 wherein: the step ofinjecting said effluent comprises injecting said effluent into aplurality of wells which have been substantially exhausted of geothermalsteam.